Remote Access issues

It’s still related to me not having remote-access — ultimately what I’m on the forums for.

This person described the issue to another person, and apparently it has to do with my provider + German Internet being bad. Would I need to directly call my ISP for them to change a setting like this, or do you know if you can do it within the router settings?

PS: I thought I found a workaround by using a VPN to host Plex with another random IP address, but it didn’t work.